The present invention relates to a calculator device for use with a camera and an electronic flash to provide the photographer with information relating the maximum distance over which he may take an acceptable photograph with his electronic flash unit with the ASA speed number of the film he is employing and the F stop setting he desires to use.
Equipment for providing information of this sort is old in the art. For example, see my U.S. Pat. No. 3,769,888, filed December 6, 1971, and issued Nov. 6, 1973, entitled "COMPUTER FLASH LIGHT SENSING APPARATUS" assigned to the assignee of the present invention. This prior art calculator generally performs the same functons as the present invention but does so with equipment which is more complicated in nature, is difficult to assemble, and which uses a relatively high number of separate pieces of equipment in order to accomplish its function. All of the disadvantages make the equipment more costly. For example, the calculator of the above referenced patent employs a base member and three separately rotatable other members, all mounted about a common axis. In order to prevent rotation of one or more of these members when other members are being rotated, a complicated arrangement of biasing springs and various locking grooves cooperating with locking teeth are provided.
An object of the present invention is to provide a simple and less costly calculator for use with a camera and electronic flash which employs fewer parts, is easier to assemble, and avoids the necessity of biasing springs and locking arrangements employed by the prior art.